When WAAAGH! Bork rampaged out of the Ghoul Stars and into the Eastern Fringe, the Wyrm-Killa tribe came with them. Festooned with alien trophies and covered in scars, this Snakebite tribe earned their name killing Tyranids. Runtherds tell tales of how the tribe were hunting through the jungles of some remote world when they came across a great fleshy spore encased in glistening amber. Dragging it back to the Ork fleet, they cracked it open and hundreds of clawed, serpentine Tyranids spilled out. The Snakebites hunted the creatures, taking great pleasure in the fact that they seemed to grow rapidly, and no sooner had you bashed one than another one appeared from a vent or drain. Before long the Ork Kill Kroozer was infested, and most of the other tribes on board were killed, only the Snakebites surviving in the weird Tyranid jungle their ship had become. By the time the infested Kroozer drifted into a star system, the Snakebites had finally killed most of the Tyranids on board, having learnt the best ways to crack them open and smash them up. Covered in Tyranid trophies and using alien claws and talons as weapons, they joined up with other Orks, calling themselves the "Wyrm-Killa" tribe. Having had so much fun hunting the Tyranids in space, the tribe had kept some alive and released them on the first world they came to. While the rest of the Orks bashed the human inhabitants the Wyrm-Killas made sure the Tyranids had time to multiply, so they would make good hunting. By the time the Orks had torn apart the humans they found themselves overrun by Tyranids, and gleefully turned their attentions to this new foe. Since then the Wyrm-Killas have spread Tyranids to dozens of worlds so they can have a good fight wherever they go."

good idea, too little dakka: fleshborers are roughly similar to bolt pistols in term of size and power; where this weapon would be too small and weak to properly represent even a shoota, the protruding gaunt head would make it extra cumbersome to count as a slugga pistol.
both speaking in terms of power and proportions, using the warrior's deathspitter would have given probably a better result as a primary weapon.

the main problem with this kind of reskins is that, while we have both fluff supporting orks weaponising tyranids (albeit full wild biomorphs) as you posted here and an old story narrating one of the first encounter between the infamous inquisitor kryptman and one tyranid relic (a fleshborer) where this last is told and shown to be able to bond and be used by non-tyranid lifeforms (effectively brainwashing the host) long after being detached from its original tyranid-companion, GW is unlikely to greenlight this heresy.

My best advice would be to either orkify a tyranid weapon OR put tyrannic trophies on an ork weapon, because I believe a tyranid trophy on a tyranid weapon is not capable enough to make the asset assimilated enough in the faction's aesthetic to be passable.

easy examples would be using this gaunt head as decoration for a normal shoota or a pokkit rokkit; while using heavy shoota assets (and perhaps a targeting squig) to form handle and various worky bitz around a tyranid warrior's deathspitter.

another very easy asset, and probably easily acceptable as well, would be to strap one of the dead hormagaunts (posed as in the garrison) in front of a shield, or a warrior's head even.

kudos for thinkin out of the box and testing the waters for tyranids cosmetics

good idea, too little dakka: fleshborers are roughly similar to bolt pistols in term of size and power; where this weapon would be too small and weak to properly represent even a shoota, the protruding gaunt head would make it extra cumbersome to count as a slugga pistol.
both speaking in terms of power and proportions, using the warrior's deathspitter would have given probably a better result as a primary weapon.

the main problem with this kind of reskins is that, while we have both fluff supporting orks weaponising tyranids (albeit full wild biomorphs) as you posted here and an old story narrating one of the first encounter between the infamous inquisitor kryptman and one tyranid relic (a fleshborer) where this last is told and shown to be able to bond and be used by non-tyranid lifeforms (effectively brainwashing the host) long after being detached from its original tyranid-companion, GW is unlikely to greenlight this heresy.

My best advice would be to either orkify a tyranid weapon OR put tyrannic trophies on an ork weapon, because I believe a tyranid trophy on a tyranid weapon is not capable enough to make the asset assimilated enough in the faction's aesthetic to be passable.

easy examples would be using this gaunt head as decoration for a normal shoota or a pokkit rokkit; while using heavy shoota assets (and perhaps a targeting squig) to form handle and various worky bitz around a tyranid warrior's deathspitter.

another very easy asset, and probably easily acceptable as well, would be to strap one of the dead hormagaunts (posed as in the garrison) in front of a shield, or a warrior's head even.

easy examples would be using this gaunt head as decoration for a normal shoota or a pokkit rokkit; while using heavy shoota assets (and perhaps a targeting squig) to form handle and various worky bitz around a tyranid warrior's deathspitter.